Circuit for space discharge devices



Jan. 19, 1932. A. E. BACHELET 1,841,394

CIRCUIT FOR SPACE DISCHARGE DEVICES Filed May 14, 1931 FIG. I

FIG; 2

INVENTOR A. 'E. BACHELE T lei MW ATTORNEY 7 devices. The invention .is applicable tosyso 7 o I g V ordinarytelephone centralofficebatteryfi is p 55 i I connected to. ground and ltsnegatlve termlnal Patented J 19, 1932 1 i1341394},1 v q ALBERT E. 'IBACHELET, or MOUNT VERNON, NEW YORK, ASSIGNOR To BELL 'rnLEPrro'HE' Lazeonnronrns, INCORPORATED, QF NEwfYoRK, Y; A GORPOBATIONOENEW YORK App cation filed May 14,

i This invention relates to circuits'for the control of the operation of spaceidisoharge tenis using any type of-space discharge device but has more especial application'to systems utilizing devices having that char-- acteristic of tion. 1

Asis well-known, space discharge devices have been constructed inwhich no space current will flow as long as the grid bias is more negative than a certain critical value; but

when the critical value is passed in a positive direction by'even a very small amount plate 5 current will rate.

flow. a substantiallyits maximum Wherever this trigger: action of space discharge devices is utll zed to actuate .slgnals,

etc., it is of very great importance thatthe source from which the grid .biasis obtained be substantiallyconstant. Otherwise fluctuations of the voltage of the source may Fig. 2 a secondforrn V The invention, as illustratedin the d raw 'ings, has particularapplication to the overflow circuit in a telephone switchboard. 111

cause false operation. g V 5 a.

The invention has as an'ob ect'c the prevendischargedevices. a

' tion of false operation-of triggertype space These andother objects and features of the invention will be apparent" ancl'the invention more clearly understood from the-follow ingdescription. together withjthe attached drawings illustrating in 7 Fig. 1 one form whichthe' take; and in invention may of the invention.

such "an arrangement it is desirablelthatja signal'be given when all of a given nuniben of trucks have been'p'ut to use.

is controlled by the operation of a trigger This, signal type space discharge. device,- the :-grid;b iasi of which is determined by the resistance asso ciated; with each 'trunkcord and the ordinary '24 volt central oflice battery; The voltage -of operation known as"trigger ac:

I A z Y of each of a series facteristic.

Another object ofithe invention isto main 1931. Serial 1%. 537,332 .7

charge, may varygif'rom 20 to 28 volts. H Referring now particularly [to Fig, 2 l the represented as having its. positive terminal connected through resistance R to a contact of jacks 4, 4, 4," mounted'on a switchboard, .[Space discharge device 5 filament or;.cathode;7 and plate oraanode i8 is of thetype liaving the triggeraction char-' device 5 v tion passage' of plate current through its winding, tov attractfits armature 10, closing havinga grid 6,

-Included in the plate circuit'ofisa relayi9 adapted upon energiZa'- this battery depending iupoii the :degr ee etc, 7

a cirouitfromjbattery 11 through signal lamp" 7 12, whereupon lamp l2is. ligl1ted .for a pur pose which will" appear hereinafter.

The vof; device; 5fis connectedltoa I point in the. circuit between resistance" :Rg-

and" j aeks: {l 4",: 4 ",1 etc; and the cathode 7 is 7 connected to" a point between two resist'anc'es R; and R 'fwhich are connected around the battery inser'ies with resistance Also Connected parallel withresistances R; and

R 'andinseries with resistance Ri. are ballast j,

lamp Bgiand resistance R ciated with jacks 4",;4, etc, contains a Y part of aresistancethevariousunits of which I: 7 are indicated as R fi Therefore, R isavariable'resistance," the unitsgof vwhich, areIeon-.

additional decreases; V 1 .As resistance and also, through resistanee R The IR'dr'op] is connected and; its; potential therefore be Assurning for the presentno change in the voltage of battery c 3," the potential of the cathode with respect to groundlre nains un-Y cha'n ged. Thegrid'biasof the device, that-is;

nect'edin parallel asthe cordsare pluggedin, I :that islunde'nthe operation of pluggingin cords the value of resistance R the potential difference between grid 6 and cathode 7 changes in a positive direction or I the grid attains a potential less negative with 7 respect to thecathode as additional cords are plugged in.

' Resistance R R etc., are chosen as to I values to correspond with the characteristics of device 5 and also in accordance with the number ofcords which are to be placed in service. These values should be such that when the last cord is plugged in, the grid bias of the device will pass its critical value and plate current will flow energizingrelay 9thereby causinglamp lQtO-light indicating that all cords are in use.v

7 By inspection, it will be seen that the potential of grid 6 must vary with varying battery voltage because changing the resistance of the units R changes the current flow through R and this would occur with varying batteryvoltagex Varying the resistance R is an essential part of the operation of the switchboard and signal arrangement; Hence it is necessary that the potential of cathode 7 change at the same rate and in thesamedh rection as that of grid with battery voltage change. The circuits inyolving resistances R R R R and R accomplish this result by niaintaining the potential difierence between grid and cathode substant ally constant. The relat onof the resistance values 1 will be seen from the following:

Assume-the battery voltage to be E at one time and E at some other time; I, with a distinguishing subscriptthe current at the time when the battery-voltage isE; and I when the battery voltage is E The resistance values will be represented by their reference characters.

Then the grid potential when battery voltageis E is E =E 3 where I is the current through R The cathode potential at the 7' I same instant is v the currents throughR and R respectively. 7 The grid bias p 1 i The change in grid bias due to change in battery voltage is The current through the ballast lamp R is constant at L regardless of battery voltage I change,

Hence l ==I +L and [g m-1'; V

subtracting 1' I" =I (2) substituting (2) in AE 7 has a" nominal value SOOw andIlmOWin-g thetube characteristics the'other resistance values may be approximated and by actual experiment the desirable'values may be obtainedl} In one-embodiment of the invention the' variousresistance values were-B 160;-

Assuming a changein batteryvoltage-of 8 volts equation (4) shows'fthatforsuchchange' the grid bias as E will be .256 voltswhich' in "the I embodiment of the invention tested I was not sufiic'ientlylarge to cause'false operation}; However, it'can be seen thatwith'but slight variations; in some-off the]resistances 1 thegridbi'as change can be made subst an tiallyjzero; T v "A's is well known discharge Vdevices'which exhibit "theJ-trigger action -tend;tojp'ern1it space-current-toflow, when once started, -re" gardless of the subsequent grid potential. The space 1 current flow can be stoppedfby opening-the space current circuit? Afterthe gridhas again reached a potential 'more eg tive than its critical valuefora a suffici'ent time to deioni'ze the "space, the plate voltage maybe again applied and the grid then has M control of the-space current asat first. Various arrangements may be devised for "accomplishing the cessation of space current" flowjandthe means about to be'describedis current of a low frequency, that is, of the order of power circuits, for example 60 cycles, g and relay 9 is an alternating current-relay. 1 Therefore when the grid has passed its critical 7 =ative than its critical value. With an alternating current plate supply, plate current will cease to flow on the negative half cycle not the only way in which this can be done, hence applicant does not 'wi sh tobe limited.

The plate supply; source 'is' alternatlng value inca positive directionandspace curthe circuit of signal 12 closed.

Whenany one. of the jacks 13, 13, etc,

, isremoved fromits associated plug the grid of device 5 will assume a potential more negand will not flow due to the grid potential on the succeeding positive half cycle. With a source of approximately cycle frequency accomplish the same purpose is shown inlFigli;

there will be sufficient time during the negative half cycle for the device tobedeionized. i Plate current therefore will cease to flow and relay 9 will release, opening the'circuit of signal 12. r v I Another circuit arrangement which j will 2. Inthis figure the features common'to both figures have been given the same referfib ence characters as in F g; g 3

the standard central oflice battery with its positive pole grounded and with parallel ciri g v I 1-.1Injangelectricalsystem in lvi ngajs'pace cuits connecting its negative. terminal to ground. One circuit includes resistance R g,

jacks l, 4, etcl, and plugs and cords contain theIresistance-ofRy. V f the-potentials of the gridiand.filament-will beiequali and some means-must be utilized to n ana'stimismnc'aqwhue'meantime,

ran R16:

cuit' iin clude'slresistances.

Resistances RgRg; a, and R g-r m a a1 cathode ne'c ted to thejalternatecorners;i

tery. 3- it will be seenjthat :with decreasing 'resistance'at R (as additional cords are plugged in'):n1ore current :fiowsthrough this branchrian'dzhence the IRIdrjop through, R "30 inc'reas'es' the grid 6 of.devic e; 5':is connecteduto'this branch at a pointbetween R t and'Bgthe-change inrthe'p'otentialiongrid 5 t -In thisvarrangement the main I I is that thevalues of resistances R 'a'n'd-R be jequ'ali Assuming a. constant voltagefor bat: V

6is'in a positive dire'ctionL .Sincethe cathode 7-is connected toja point between X resistances R and'R andjthe current flowing through these resistances does not change with .va'ria tionin Rg thepotential ofs-th'e cathode re-* a; 1n.ainsfcons'tant-.- -Asi n Figul'thevalues'are so 7 chosen that whenl't'he last available cords "is pluggedin the potential of grid (iis changed sufficiently to, permit jplate current to; flow j whereby relay is energized an-di the corree sponding si'gnal given.

With a fixed value of resist since for B and ,the v alues of resistances R 1 and R equal5 -aj 1 changecinivoltage "ofbattery'3 will causem change in current 'ffiow'rth'rough thebranches ofithebridge but nojrelative change.1 Hence ,whereasthe potentials'ofgrid 6 and cathode will change relative to ground, their potent-f tial difference grid bias) remains unchanged 7 I false operation of theisystemz r I and bagter y; voltage. change; will-notcause to insure ahias :on thegridundercertain con; dItI OI lS ofresistance values. ForeXample; 1f.

is {equal tothatof R keepfthe 1 at "a potential-more. negative;

thankits critical value until theivalueuof Ere 'sistance R reachesgthat required to make the grid more positive than its critical value. I: As in Fig; lthe-plateburirent source 15is, alternatingicurrentofa lowfrequency. "The t operationfiof relay '9 and the 1nanner':of=de-; 3

' 11 Itifis to be .understoodithat whereas the. cventionieis illustrated in connection with one onizing space discharge devicej5yis the same 'circuitof a telephone; switchboard-the linven i tionitself is. capable of being:appliedto any device; 4 The invention, therefore, is tofloe lim;

:Whatii .c aimedis discharge. devi e-hav ng ridsho plategelectrodesya battery, a-divided circuit discharge device having of resistances connected across said battery,-

connections from said grid and cathodeto diiferentpoints on said resistances fwhereby 7 current'fiow from saidsbattery establishes a 7 potential difference betweenisaidygrid and said. cathode and means including said-resistanc'es for maintainingthis potential dii'ie terence substantiallyconstant, with change,

, in the voltage of-said battery. ,7 V 1' N 2.. In an electrical system involving a space discharge device having grid, cathode and plate electrodes, abattery, circuit means whereby :current .flow *from said battery establi'shes a potential difierence betweensaid cathode and said grid, including means operating iii-response to change ot voltage .ot

I said battery to cause a proportionate change in the, potentials of each of said electrodes whereby their difference in potentialremains substantially constant. V ,7 Q '3L11n anv electrical systeminvolving aspace grid, cathode and plate electrodes, abattery, parallel circuit branches through which current from said battery "flows, said grid being connected "to one of said branches and said cathode con nected to another of said branches-and resistance units in said branchesso disposed that the potential dili'erence between said grid and-said cathodezremains substantially constant with varying battery voltage.

p 4. In an electrical system involving aspace discharge device having plate electrodes, 'a battery, cuits associated with said battery,

said device being'conn'ected to one-70f said circuits at a pointbetweentwo resistances in- -cluded in'said circuit',zthefcathode being connected betweenqtwo resistances included in another of said :circuits' and ,a third circuit a plurality of cir containing a ballastilamp in parallel tosaid second circuit.

5.111 a telephone movable contact m'enibers for connecting circuits. through' said switchboard, resistance grid, cathode and V the 'gridrof i i menace of said space discharge device whereby the anode current flow -therethroi1gh is varied causing the operationof sa signalrdevice. V

7. In a telephone switchboard incombina: tion, a space discharge device, a battery, a plurality of j acks,,a;plurality ofcord circuits including plugsforinsertion in said jacks, a

resistance unit -in'oeach cord circuit, a circuit including said battery, said jacks and said cord circuits to which the grid of/said space discharge device-is connected, and other circuits associated with :said battery and said space discharge device whereby the'gridbias of said space discharge. device is varied by said cord circuit resistance. irrespective of said batteryvoltage to cause the operation of a signal device. 1

v -8. In a telephone switchboard, a signal means comprising, a-space dischargedevice, a signal-device included inthe anodecircuit of said spacedischarge device, a plurality of cord circuits, a resistance unit in each cord circuit, and means whereby said cord circuits as'they are utilized cause a change in the grid bias of said space discharge-device of such a degree that when the last available cord circuit is used the grid 'biasis such as to cause sufficient anode-current to' flow to operate said signaldevice. q 7 In witness whereof, I hereunto subscribe my name this 12thday of May, 1931. v

\ ALBERTE. BACHELET,

switchboard, iixed and i means associated with saidmembers,raspace discharge device, a battery, connections whereby said .battery-and-said resistance means cooperateito' vary the grid biasot said vice latter a given number ot said contact members are operated, T

V 6. In a-telephone switchboardin' combina- 65. battery varied to vary the grid potential space discharge device to causeanode current to. fiowrtherethrough to operatea signal de-- ti'on,a b attery, a space discharge device, jacks 

